A genetic study of a discrete, isolated population with respect to a complex of developmentally and educationally important variables is proposed. A number of colonies of the Hutterite sect, which numbers approximately 20,000 individuals, will be investigated in collaboration with the University of Colorado Medical School, which is studying linkage, recombination and genetic disease among these people. The population constitutes a literate, non-mobile group in which all generations are represented locally, which does not practice birth control, and which has exhaustive geneological and vital statistics records, uniform living conditions, no in-migration and virtually no illegitimacy. Upwards of fifty biochemical and cytogenetic markers will be typed for each individual. The behavioral variables of interest include spatial and verbal ability, speech acquisition and reading skills, field dependence, ideational fluency, automatization, handedness and ear dominance for speech and non-speech sounds. The principal analytic approach to be employed is the detection and mapping into the appropriate linkage groups of as many major genes as possible which have a substantial influence on the behavioral traits. The parameters of the appropriate pedigree, linkage, psychometric and factor analysis models will all be estimated by the method of maximum likelihood. In addition, the relationship of the indices of functional specialization of the hemispheres of the brain to cognitive and motor performance will be investigated at the population level for the very first time, emphasizing factor structure and the developmental sequence of events. The proposed program of research constitutes a rare opportunity to bring strict genetic control to the field of human behavioral science and to predict and provide counseling in advance for certain developmental abnormalities on the basis of inferred behavioral genotype.